Vacuum tube



K. OKABE VACUUM TUBE Nov. 12, 1929.

Filed May l1, 1926 Fig 64l A HJ e ra n OK w LCM L D e O www ,im H

H .n n W MJ im wd .9M Mee @Z cam Pq/V /al V 6 Patented Nov. 12, 1929 PATENT OFFICE KINJIRO OKABE, 0F SEND'AI, JAPAN VACUUM TUBE Application led May 11, 1926, Serial No. 108,406, and in Japan March 5, 19.26.

My invention relates to vacuum tubes and more particularly to types of vacuum tubes having multiple electrodes to be used as am,- pliiers or oscillators and the like.

The object of my invention is to provide an improved vacuum tube of superior character whereby the internal resistance can be remarkably reduced resulting in a great increase of anode current and also mutual con- 0 ductance which is the ratio of the amplification constant divided by the internal resistance. v

An ordinary vacuum tube of three electrodes comprises a plate, a filament and a 5 grid, and these elements are usually connected between the terminals of batteries and. also to an oscillating circuit consisting of inductance and capacity though not necessarily limited thereto. Such triode vacuum tubes are known as a pliotron. My invention has reference to such kinds of vacuum tubes and is characterized by the feature that an auxiliary anode is provided and also the plates are specially arranged so that elec- 5 trons may pass freely between them. In other words, according to my invention the secondary emission of electrons is utilized in a particular way, and the vacuum tube embodying my invention may be known as an excited vacuum tube which emits secondary electrons excited by primary electrons, or it may also be termed as a secondary electron vacuum tube. There is a certain class of vacuum tubes known as dynatrons which also utilizes the secondary emission of electrons but they differ from that of my inven-l tion both in principle and operation. The excited vacuum tube so called rather resembles the ordinary triode, but the mutual conductance of the excited vacuum tube is a few times larger than that of the triode if compared under, the same conditions. I have obtained satisfactory results in successfully operating the excited vacuum tube as an oscillator or an amplifier. The mutual conductance is the most important factor determining the superiority of a vacuum tube and if it is larger it gives remarkable improvement in the character of a vacuum tube.

For a better lunderstanding of my invention, reference is had to the following description taken in connection with the accompanying drawing, in which Fig. 1 diagrammatically illustrates a four element vacuum tube embodyingmy invention; Fig. 2 is a side view; Fig. 3 is a side view of a modified form having a cylindrical anode; Figs. 4 and 5 illustrate these vacuum tubes in perspective views, and Fig. 6 is a diagrammatic elevational view of a tube embodying the invention.

The novel features and combinations which I believe to be characteristic of my invention are pointed out with particularity in the appended claim.

Referring now, more particularly to the drawings, es ecially Figs. l and 2, the vacuum tube em odying my invention comprises essentially a filament F, a grid G, a plate P and a secondary plate or auxiliary anode S. A suitable number of these elements may be adopted and it will be evident from these figures that a number of plates P which constitute anodes of this vacuum tube corresponding to the anode of an ordinary triode are arranged in spaced relation with each other and extremely near to the auxiliary anode S and each of these anodes P is located so that its vane tip subtends a certain angle 0 against the common normal between the filament and auxiliary anode as seen more clearly from Fig. 1. This is the most essential feature of my invention. In this case I have used plane anodes and found that a better result can be obtained by making the auxiliary anode S of aluminium for moderate size but it should be made of some other metal in a larger power unit as aluminium melts away in such cases. I have found that the emission of the secondary electrons can be greatly increased by coating the surface of such auxiliary anode with nickel oxide and tungsten oxide. In carrying this into effect I have found it most convenient to use grids G and plates P made of nickel and a tungsten filament F, then evacuate the tube and send in a little air or oxygen and allow the electric current to pass through them,

then the oxides formed will naturally adhere to the auxiliary anode S to a high degree,

, thoughsome oxide attached to the late give `a better eject. 'lfn thev'mod' ed -form' of the excited vacuum tube so called shown" in Figs. 3 and 5 the auxiliary anode S is made in a cylindrical form and the plates P/ are arranged along its inner periphery and the grid is located around the filament F which is placed at the centre of the tube. 'The plates P, should essentially be placed extremely near the auxiliary anode S and each vane may be arranged either radially or at a small angle 6 with the radius if desired. in this case the radius means a common normal line between the circumference of S and the axis of F.

rlhe principle of operationmf the vacuum tube embodying my inventionv as arranged `and constructed as above is as follows :y

Electrons from the lament F are put inY motion by theelectric iield 'between F and P and all of thethermo-electrons as accelerated by the anode P will pass through the space between the anodes P until they impinge on the auxiliary anode S, and then the secondary electrons are emitted from this anode S. ln

order that all of the emitted secondary elec'- trons can beabsorbed by the plates P, the distance between P and S small.

lhe number ci is made extremely the. secondary electrons is very much more than the number of primary electrons. These secondary electrons are liable to be attracted further to the positive anode P. Thus the number of electrons 'dowing to the anode P will be a 'few times greater than that of the primary electrons issued from F. As the Whole electron current flow- -ing through P can be controlled by the grid G, the vacuum tube or special triode according to the present invention hase very large mutual conductance.

As it is evident from the foregoing Athe vacuum tube according to my invention is characterized b the feature that the plate current or ano e current is remarkably increased to about 2 to 3 times andless heat is generated inthe vacuum tube. This latter feature is due to the fact. that the size of lament can be greatly reduced according energy, but a considerable energy is spent for emitting secondary electrons, so aluminium plates can be used in moderate size as already stated. As the thermo-electron passes in a direction parallel tothe surface of the plate P the operation of the vacuum tube according to my invention will be somewhat varie if "my invention.

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magnetic iield is appliedto it, but it rather belongs to the other special application of For a better understanding of my invention will briei ex lain the principal dinerence between t e gown ty e of vacuum tubes such as ,dynatron and tlie super-triode according to my invention. Since in the dynatron the current passing through the electrode S is utilized it has the characteristic of negative resistance or of falling character, while in .the .present invention the current ,through the plates is utilized and therefore forms as a spiral wire, a perforated cylinder or a squirrel cage, all of which are quite different from that of my invention. It will be evident from the foregoing that my invention is clearly different from so-called dynatron both in principle and operation as well -as in its construction without anyl further description.

in accordance with the provisions of the patent statutes I have described the principle oi operation of my invention together with the apparatus which I now consider to represent the best embodiment thereof but I would have it understood that the apparatus shown is only illustrative and that the invention may be carried out by other-means.

What Il claim as new and desire to secure y by Letters Patent of the United States, is:

A vacuum tube comprising `a iilament, a

control grid spacedly disposed on veach side of said lament, main anodes spacedly disposed adjacent the outward sides of said grid and aluminum auxiliary anodes coated with nickel oxide and tungsten oxide spacedly disposed adjacent the outward sides of said main anodes whereby the variation in the anode voltage directly depends uon the primary electron current from the ament and the current in the main anode. Y

ln witness whereof, I have hereunto set my hand this twenty-.second day of March, 1926. f

KINJRO OKABE.

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